problems with Lua match to find a pattern - lua

Question

I'm struggling with this problem:
Given 2 strings:
s1 = '/foo/:bar/oof/:rab'
s2 = '/foo/lua/oof/rocks'
I would like to produce the following information:
If they match (these two above should match, s2 follows a pattern described in s1).
A table holding the values of s2 in with the corresponding name in s1. In this case we would have: { bar = "lua", rab = "rocks" }
I think this algorithm solves it, but I can't figure how to implement it (probably with gmatch):
store the placeholders : indexes as KEYS of a table, and the respective VALUES being the name of these placeholders.
Example with s1:
local aux1 = { "6" = "bar", "15" = "rab" }
With the keys of aux1 fetched as indexes, extract the values of s2
into another table:
local aux2 = {"6" = "lua", "15" = "rocks"}
Finally merge them two into one table (this one is easy :P)
{ bar = "lua", rab = "rocks" }

Answer 1

Something like this maybe:
function comp(a,b)
local t = {}
local i, len_a = 0
for w in (a..'/'):gmatch('(.-)/') do
i = i + 1
if w:sub(1,1) == ':' then
t[ -i ] = w:sub(2)
else
t[ i ] = w
end
end
len_a = i
i = 0
local ans = {}
for w in (b..'/'):gmatch('(.-)/') do
i = i + 1
if t[ i ] and t[ i ] ~= w then
return {}
elseif t[ -i ] then
ans[ t[ -i ] ] = w
end
end
if len_a ~= i then return {} end
return ans
end
s1 = '/foo/:bar/oof/:rab'
s2 = '/foo/lua/oof/rocks'
for k,v in pairs(comp(s1,s2)) do print(k,v) end

Answer 2

Another solution could be:
s1 = '/foo/:bar/oof/:rab'
s2 = '/foo/lua/oof/rocks'
pattern = "/([^/]+)"
function getStrngTable(_strng,_pattern)
local t = {}
for val in string.gmatch(_strng,_pattern) do
table.insert(t,val)
end
return t
end
local r = {}
t1 = getStrngTable(s1,pattern)
t2 = getStrngTable(s2,pattern)
for k = 1,#t1 do
if (t1[k] == t2[k]) then
r[t1[k + 1]:match(":(.+)")] = t2[k + 1]
end
end
The Table r will have the required result
The solution below, which is some what cleaner, will also give the same result:
s1 = '/foo/:bar/oof/:rab'
s2 = '/foo/lua/oof/rocks'
pattern = "/:?([^/]+)"
function getStrng(_strng,_pattern)
local t = {}
for val in string.gmatch(_strng,_pattern) do
table.insert(t,val)
end
return t
end
local r = {}
t1 = getStrng(s1,pattern)
t2 = getStrng(s2,pattern)
for k = 1,#t1 do
if (t1[k] == t2[k]) then
r[t1[k + 1]] = t2[k + 1]
end
end